build: fix 'make distcheck'

CC       src/systemd/src/basic/src_libsystemd_nm_la-string-table.lo
 ../../src/systemd/src/basic/parse-util.c:30:10: fatal error: 'errno-list.h' file not found
 #include "errno-list.h"
         ^~~~~~~~~~~~~~

Fixes: 1a2419a0c9

Makefile.am

@@ -1212,6 +1212,7 @@ src_libsystemd_nm_la_SOURCES = \
 	src/systemd/sd-adapt/def.h \
 	src/systemd/sd-adapt/dirent-util.h \
 	src/systemd/sd-adapt/env-util.h \
+	src/systemd/sd-adapt/errno-list.h \
 	src/systemd/sd-adapt/format-util.h \
 	src/systemd/sd-adapt/gunicode.h \
 	src/systemd/sd-adapt/ioprio.h \